Intestine epithelial cells are in direct contact with foods, enteric bacteria, pathogens and the like. They do not simply function as a physical barrier, but also play an important role in the induction of and giving direction to immune responses in the intestine, and the like. Intestine epithelial cells form a structure wherein intercellular spaces are closely adhered by plural tight junction-related factors such as ZO-1, Occludin and Claudin firmly. When the expression of said related factors decreases and the like in the intestinal epithelial cells due to IL-6, TNF-α, insulin and the like, the intestinal tract barrier function may sometimes be damaged (non-patent document 1). Also, when the intestinal epithelial cell layer is damaged by pathogen and the like, peripheral immunocytes are activated to repair the epithelial layer and remove foreign substances.
However, when immune response becomes excessive, inflammation may occur in the intestinal tissues and, as a therapeutic agent to suppress such inflammation, a therapeutic agent for inflammatory bowel diseases, which contains lactobacillus bacterium, and the like have been reported (patent document 1). As a therapeutic drug that suppresses permeation of allergen substances and the like by taking note of substance permeation through tight junction and preventing looseness of the tight junction, intestinal tract-protecting agents containing whey protein, casein, serum albumin and the like as an active ingredient and the like have also been reported (patent document 2).
While the above-mentioned intestinal tract-protecting agents have been reported, the development of a new intestinal tract-protecting agent, which can be used for the prophylaxis or treatment of damage in intestinal tract barrier function or diseases caused thereby is desired.
Conjugated fatty acid represented by conjugated linoleic acid (CLA) has been reported to have various physiological activities such as a lipid metabolism improving effect, an anti-arteriosclerosis action, a body fats decreasing action and the like (non-patent documents 2-4), and is a functional lipid expected to be applicable to various fields of medicament, functional food and the like. In addition, action on the intestinal tract protection has been attracting attention and improvement of symptoms of patients with ulcerative colitis such as Crohn's disease and the like, by conjugated linoleic acid has been reported and the like (http://www.nimml.org/838/).
Conjugated linoleic acid is produced as an intermediate of saturation metabolism of unsaturated fatty acid by lactobacillus. As an intermediate of the metabolism, for example, hydroxylated fatty acids such as 10-hydroxy-cis-12-octadecenoic acid, 10-hydroxy-octadecanoic acid and the like, oxofatty acids such as 10-oxo-12-octadecenoic acid, 10-oxooctadecanoic acid, 10-oxo-11-octadecenoic acid and the like, and the like exist. However, there is no report on the action and effect of an intermediate of saturation metabolism of unsaturated fatty acid by lactobacillus on the intestine, as far as the applicant is aware of.